Prior art workers have addressed the problem of tool mark formation when a boring tool is withdrawn from a finished bore after machining. Illustrative of these efforts is U.S. Pat. No. 2,368,846 which issued Feb. 6, 1945 of common assignee herewith and which elastically deforms a hollow boring bar by action of a centrifugal weight acting through a lever disposed inside the bar. When the boring bar is rotated, the centrifugal weight on one end of the lever causes the other end of the lever to exert a radial force on the hollow boring bore to elastically deform it to a cutting position. When rotation of the tool is stopped after machining, the lever force is removed and the resiliency of the boring bar causes it to return to a radially retracted position out of contact with the finished bore to avoid tool mark formation during tool withdrawal. U.S. Pat. Nos. 2,412,038 issued Dec. 3, 1946 and 3,744,923 issued July 10, 1973, also of common assignee herewith, both utilize an elastically deformable component in the boring tool construction to position the tool element between the cutting position and retracted position. For example, the earlier of these patents elastically deforms the web portion of a bell-shaped tool holder by a hydraulically actuated rod engaging an eccentrically disposed recess in the tool holder while the later issued patent elastically deforms a flexible diaphragm to which a tool support is affixed. And, U.S. Pat. No. 3,296,898 issued Jan. 10, 1967 employs a sliding cam action between a hydraulically actuated rod and a tool-carrying body to tilt the latter off its axis of revolution against an elastomeric ring for tool retraction purposes. U.S. Pat. No. 3,391,585 issued July 9, 1965 of common assignee herewith uses a cam mechanism to flex a T-shaped tool carrier.
Other patents which relate to boring tools having various types of mechanisms for adjusting the position of a tool element are as follows:
U.S. Pat. No. 3,433,104 issued Mar. 18, 1962 PA1 U.S. Pat. No. 3,625,625 Dec. 7, 1971 PA1 U.S. Pat. No. 3,749,508 issued July 31, 1973 PA1 U.S. Pat. No. 3,918,826 issued Nov. 11, 1975 PA1 U.S. Pat. No. 4,260,303 issued Apr. 7, 1981
An adjustable collapsing tap and an adjustable threading die are described in U.S. Pat. No. 909,749 issued Jan. 12, 1909 and U.S. Pat. No. 992,903 issued May 23, 1911, respectively.